1i.ifft(1) GRASS GIS User's Manual i.ifft(1)
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6 i.ifft - Inverse Fast Fourier Transform (IFFT) for image processing.
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9 imagery, transformation, Fast Fourier Transform
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12 i.ifft
13 i.ifft --help
14 i.ifft real=name imaginary=name output=name [--overwrite] [--help]
15 [--verbose] [--quiet] [--ui]
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17 Flags:
18 --overwrite
19 Allow output files to overwrite existing files
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21 --help
22 Print usage summary
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24 --verbose
25 Verbose module output
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27 --quiet
28 Quiet module output
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30 --ui
31 Force launching GUI dialog
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33 Parameters:
34 real=name [required]
35 Name of input raster map (image fft, real part)
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37 imaginary=name [required]
38 Name of input raster map (image fft, imaginary part
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40 output=name [required]
41 Name for output raster map
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44 i.ifft is an image processing program based on the algorithm given by
45 Frigo et al. (1998), that converts real and imaginary frequency space
46 images (produced by i.fft) into a normal image.
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49 The current mask is respected when reading the real and imaginary com‐
50 ponent files; thus, creating a mask is a primary step for selecting
51 the portion of the frequency space data to be included in the inverse
52 transform. The module wxGUI vector digitizer can be used to create
53 masks while viewing the real or imaginary component image. Alterna‐
54 tively r.circle can be used to generate high-, low- and donut filters
55 specifying the DC point as circle/ring center. When i.ifft is executed,
56 it (automatically) uses the same GRASS region definition setting that
57 was used during the original transformation done with i.fft.
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60 i.cca, g.gui.iclass, i.fft, i.pca, r.circle, wxGUI vector digitizer
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63 · M. Frigo and S. G. Johnson (1998): "FFTW: An Adaptive Software
64 Architecture for the FFT". See www.fftw.org: FFTW is a C sub‐
65 routine library for computing the Discrete Fourier Transform
66 (DFT) in one or more dimensions, of both real and complex data,
67 and of arbitrary input size.
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69 · Richards, J.A (1986): Remote Sensing Digital Image Analysis,
70 Springer-Verlag, 1986.
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72 · Personal communication, between program author and Ali R. Vali,
73 Space Research Center, University of Texas, Austin, 1990.
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76 David Satnik, GIS Laboratory, Central Washington University
77 Glynn Clements (FFTW support)
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80 Available at: i.ifft source code (history)
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82 Main index | Imagery index | Topics index | Keywords index | Graphical
83 index | Full index
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85 © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
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89GRASS 7.8.5 i.ifft(1)